Tutorial how to set up a aliexpress industrial modbus display.
Usually you can search for following listings: “0.56 in 4 Digit LED Display RS485 Serial Port Meter Communication RTU/ASCII Protocal”

 

So first the specs:



  1. Support ASCII text and RTU dual protocol automatic identification, no user setting in required.
  2. The meter can display 4 digit of serial port.
  3. Wide range of power supply voltage between DC7~36V.
  4. Large 0.56inch display area for only 4 digit ,more clear.
  5. The baud rate can be 1200bps/2400bps/4800bps/9600bps/19200bps/38400bps/57600bps/119200bps.
  6. Price 10-15 USD (12.2021)

Because display will come without any manuals or information, it was quite a hassle to find good information about the display.

 

Things we need:

1 ) RS485 TO USB converter


2 ) QModMaster Software https://sourceforge.net/projects/qmodmaster/files/

3) Termite Terminal https://www.compuphase.com/software_termite.htm

 

 

From behind without the cover the display looks like following:

Step 1:

Connect your RS485 converter with display. B- with B- and A+ with A+
Connect power for the display.

If RS485 converter is recognised by your computer, we can continue.

 

Step 2:

Lets open TermiteTerminal software:

Open settings and configure like following, remember to use right COM port:

 

Step 3:

Now we will ASCII mode to communicate with the display.

Try out following commands to make sure the connection between computer and display is established.

Serial response test:
$001,01&

Check digital mode:
$001,02&

If you receive following answers everything works as it should:

You can use ASCII to control the display:

Displays 12.14
$001,12.14&

Displays abc
$001,abc$

If everything worked we can proceed with the next step.
Close the Termite software.

Step 4:

Lets open QModMaster software:

Next lets configure QModMaster settings. Check on which COM port is used for the RS485 converter.
In QModMaster go “Options” -> “Modbus RTU”. Except for COM port your settings should be following:

Input Settings and click “OK”.

Step 5:

Now click on small connect icon:

Step 6:

Display modbus registers are following:

Decimal point:
Slave Addr: 1
Function: 0x06
Start Address: 4

Value:
Slave Addr: 1
Function: 0x06
Start Address: 0

So inserting 2 to the register 4 and 1001 to register 0 and writing the values will show 10.01:

Step 7:

You can also use multiple registers to indicate values on the display.

Value:
Slave Addr: 1
Function: 0x10
Start Address: Hex:0x90 / Dec:144
Number of Registers: 2

Values 2 and 1001 will display 10.01
Values 1 and 6006 will display  600.6

The first register is used for indicating decimal point and sign. Hex values for different options are as following:

 

Hex
00XX = +
01XX = –

XX00 = xxxx
XX01 = xxx.x
XX02 = xx.xx
XX03 = x.xxx

 

And that is it.

Additional information found on internet: